(1) Field of the Invention
The present invention relates to a shaped polyphosphazene article and a process for producing the same. More particularly, the present invention relates to a shaped polyphosphazene article having a surface portion thereof modified without degrading the inherent properties of the phosphazene polymer and having improved surface properties, and a process which can be utilized industrially for producing the same.
(2) Description of the Related Art
It is known that a polyphosphazene is an elastomer having a backbone chain consisting of phosphorus and nitrogen atoms and not containing a carbon atom, and therefore, exhibiting an excellent heat resistance and chemical resistance. The polyphosphazene polymer can be shaped into desired shapes, for example, a sheet, a film, a wire, and a filament, as disclosed in Japanese Unexamined Patent Publication Nos. 60-87,829 and 60-156,505.
Attempts have been made to provide a polyphosphazene polymer having an enhanced abrasion resistance, oxidation-resistance or affinity to living organisms by attaching a specific type of side chains to the backbone chain of the polymer. However, the attempted polyphosphazene polymers sometimes exhibit disadvantageous properties, for example, a degraded stability during the shaping procedure, or a deteriorated chemical property, physical property and/or dynamic property.
It is also known from "Macromolecules", Vol. 5, No. 2, page 231, 1972, that all or some of the side chains in a polyphosphazene polymer can be converted to a different type of side chains by heat treating the polyphosphazene polymer in a solution containing a compound capable of imparting the different type of the side chains. However, the resultant modified phosphazene polymer has the same disadvantages as those mentioned above.